A method and apparatus for operation by an access point (AP) is provided. The method may comprise receiving a first frame from a first STA, the first frame including first data and receiving a second frame from a second STA, the second frame including second data. In response to the receiving, an acknowledgement (ACK) frame may be transmitted to the first STA and to the second STA. The ACK frame may be addressed to a broadcast address and include a field which indicates whether the ACK frame is a multiple traffic identifier (multi-TID) block ACK frame format or another ACK frame format.